1. Field of the Invention
The present invention generally relates to hand tools and, more specifically, to an adjustable safety utility knife with slip resistant elements.
2. Description of the Prior Art
Utility knives are widely used in construction, business and hobby applications for cutting such materials as paperboard, wallboard, tiles, string and other objects. Typically, such utility knives are in the form of an elongate hollow housing that can be gripped by the user along an intermediate portion thereof and into which there are placed trapezoidal flat cutting blades. The blades typically have a single cutting edge. The blade is typically slidably mounted on a carrier for movement between a retracted position within the housing and an extended position in which the cutting edge is at least partially exposed through a front end aperture or slot, the carrier being coupled to a manually operated element, such as a button positioned in a manner convenient to be actuated by the user""s hand.
Many utility knives include a region within the housing for storing one or two additional blades that can be used to replace the operative blade when it becomes dull. In most cases a screw or similar means is used for attaching the two clam shell members together during normal use. When blades need to be replaced, the screw is removed, allowing to two shell members to be separated, and access is provide to the replacement blades.
While the flat cutting blades used in utility knives are relatively thin, substantial frictional forces are frequently applied to or exerted on these blades, such as when the blades are used to cut heavy or thick cardboard, wallboard or the like. As typically used, the utility knives are placed on the material to be cut and, with the blade penetrated through the material, and with the user""s hand extended, the utility knife is pulled toward the user to effect the cutting. The frictional forces resulting on the blade are such as to pull on the utility knife in the opposite direction, tending to pull the utility knife out of the hand of the user. It is desirable that the user continue to maintain a good grip on the utility knife for safety reasons as well as to prevent damage to the workpiece being cut. Known utility knives, however, are typically made of metallic housings which provide a limited amount of friction between the exterior surface of the housing and the user""s hand. Attempts have been made to increase the amount of friction available for this purpose by texturing the surface by providing ribs, knurling, etc. While such textured surfaces have somewhat increased the ability of the user to grip the utility knife housing, the greater the surface irregularities to enhance the gripping action, the more uncomfortable the knife is to use as any such surface irregularities tend to penetrate the skin of the user when the knife is tightly gripped to overcome the pulling frictional forces on the blade.
Accordingly, it is an object of the present invention to provide an adjustable safety utility knife which does not have the disadvantages inherent in known utility knives.
It is another object of the present invention to provide an adjustable safety utility knife which is simple in construction and economical to manufacture.
It is still another object of the present invention to provide a safety utility knife as in the previous objects which enhances the frictional grip to a user of the utility knife housing to counteract the pulling forces on the blade during cutting.
It is yet another object of the present invention to provide an adjustable safety utility knife as in the present invention which is comfortable to the user, substantially independently of the tightness of the grip by the user on the handle on the knife.
It is a further object of the present invention to provide an adjustable safety utility knife which is safe and convenient to use and minimizes the probability that the utility knife will be inadvertently or accidentally pulled out of the user""s hand when cutting thick or heavy objects.
It is still a further object of the present invention to provide an adjustable safety utility knife which provides the user added control over the knife during use, particularly during cutting of thick or heavy objects, thereby minimizing the probability of damage to the material being cut.
In order to achieve the above objects, and others which will become apparent hereinafter, an adjustable safety utility knife in accordance with the present invention comprises an elongated ergonomically shaped handle formed of two elongate shell members, each having a peripheral edge and an outer convex surface and an inner generally concave surface. Fastening means is provided for fastening such shell members at said peripheral edges along a vertical parting plane to form an elongated internal cavity. Said handle defines a front end, a back end and an intermediate portion suitable for being gripped by a user and also defining top and bottom surfaces extending along opposite sides of said front end substantially aligned with said parting plane and dimensioned for passage of a flat cutting blade therethrough. Guide means is provided within said elongated cavity for guiding the cutting blade between a first position for safely storing the blade fully inside said cavity and a second position for selectively extending the blade beyond said aperture to expose at least a portion thereof A manually operated button is arranged on said top surface and coupled to said guide means for selectively moving the blade between said first and second positions. Slip resistant means is provided secured to said shell along said top and bottom surfaces between a rearmost operative position of said manually operated button and said back end. Such slip resistant means generally conforms to said outer convex surface and enhances gripping of said handle and minimizes slippage of said handle during use of the utility knife when gripped by a user.